auto-update: make output more user friendly

The rather raw and scarce output of `podman auto-update` has been a
thorn in my eyes for a longer while.  So far, Podman would only print
updated systemd units, one per line, without further formatting.

Motivated by issue #9949 which is asking for some more useful
information in combination with a dry-run feature, I sat down and
reflected which information may come in handy.

Running `podman auto-update` will now look as follows:

```
$ podman auto-update
Trying to pull [...]

UNIT                    CONTAINER            IMAGE                   POLICY      UPDATED
container-test.service  08fd34e533fd (test)  localhost:5000/busybox  registry    false
```

Also refactor the spaghetti code in the backend a bit to make it easier
to digest and maintain.

For easier testing and for the sake of consistency with other commands
listing output, add a `--format` flag.

The man page will get an overhaul in a follow up commit.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

1 files changed, 20 insertions, 4 deletions

diff --git a/docs/source/markdown/podman-auto-update.1.md b/docs/source/markdown/podman-auto-update.1.md
index 24b910470..4f2608be4 100644
--- a/docs/source/markdown/podman-auto-update.1.md
+++ b/docs/source/markdown/podman-auto-update.1.md
@@ -41,6 +41,22 @@ If the authorization state is not found there, `$HOME/.docker/config.json` is ch
 
 Note: There is also the option to override the default path of the authentication file by setting the `REGISTRY_AUTH_FILE` environment variable. This can be done with **export REGISTRY_AUTH_FILE=_path_**.
 
+#### **--format**=*format*
+
+Change the default output format.  This can be of a supported type like 'json' or a Go template.
+Valid placeholders for the Go template are listed below:
+
+| **Placeholder** | **Description**                        |
+| --------------- | -------------------------------------- |
+| .Unit           | Name of the systemd unit               |
+| .ContainerName  | Name of the container                  |
+| .ContainerID    | ID of the container                    |
+| .Container      | ID and name of the container           |
+| .Image          | Name of the image                      |
+| .Policy         | Auto-update policy of the container    |
+| .Updated        | Update status: true,false,failed       |
+
+
 ## EXAMPLES
 Autoupdate with registry policy
 
@@ -53,7 +69,7 @@ bc219740a210455fa27deacc96d50a9e20516492f1417507c13ce1533dbdcd9d
 
 ### Generate a systemd unit for this container
 $ podman generate systemd --new --files bc219740a210455fa27deacc96d50a9e20516492f1417507c13ce1533dbdcd9d
-/home/user/containers/libpod/container-bc219740a210455fa27deacc96d50a9e20516492f1417507c13ce1533dbdcd9d.service
+/home/user/container-bc219740a210455fa27deacc96d50a9e20516492f1417507c13ce1533dbdcd9d.service
 
 ### Load the new systemd unit and start it
 $ mv ./container-bc219740a210455fa27deacc96d50a9e20516492f1417507c13ce1533dbdcd9d.service ~/.config/systemd/user
@@ -67,7 +83,7 @@ $ systemctl --user start container-bc219740a210455fa27deacc96d50a9e20516492f1417
 
 ### Auto-update the container
 $ podman auto-update
-container-bc219740a210455fa27deacc96d50a9e20516492f1417507c13ce1533dbdcd9d.service
+[...]
 ```
 
 Autoupdate with local policy
@@ -80,7 +96,7 @@ be0889fd06f252a2e5141b37072c6bada68563026cb2b2649f53394d87ccc338
 
 ### Generate a systemd unit for this container
 $ podman generate systemd --new --files be0889fd06f252a2e5141b37072c6bada68563026cb2b2649f53394d87ccc338
-/home/user/containers/libpod/container-be0889fd06f252a2e5141b37072c6bada68563026cb2b2649f53394d87ccc338.service
+/home/user/container-be0889fd06f252a2e5141b37072c6bada68563026cb2b2649f53394d87ccc338.service
 
 ### Load the new systemd unit and start it
 $ mv ./container-be0889fd06f252a2e5141b37072c6bada68563026cb2b2649f53394d87ccc338.service ~/.config/systemd/user
@@ -102,7 +118,7 @@ $ podman commit --change CMD=/bin/bash inspiring_galileo busybox:latest
 
 ### Auto-update the container
 $ podman auto-update
-container-be0889fd06f252a2e5141b37072c6bada68563026cb2b2649f53394d87ccc338.service
+[...]
 ```
 
 ## SEE ALSO